I am sick of failing amplifiers

[microstrip]

I don't know at 1987 are 105°types already existed, some had esr over 100ohms i change all after 38 years. protection works fine at 0.44 ohms the relay switches off the output until then full class A power.

Are you sure of this ESR value? An electrolytic with an ESR over 100 ohms was not a capacitor any more since long! Good quality electrolytic capacitors have an ESR between 10 and 100 mohms.

I can't understand what you mean with 0.44 ohms and class A.

sounds amazing good after refresh. with a high damping factor over 15000 in the bass normaly sounds this dry this amp not. Love this oven

Curious. I ask myself how could they measure an output impedance of .5 mohm?

 

[DasguteOhr]

Are you sure of this ESR value? An electrolytic with an ESR over 100 ohms was not a capacitor any more since long! Good quality electrolytic capacitors have an ESR between 10 and 100 mohms.

470uf has only 0. 1uf /101 ohms after 38years leaky underneath

I can't understand what you mean with 0.44 ohms and class A.

Minium load that can drive the amp at the speaker output before it goes in protection with full power..

Curious. I ask myself how could they measure an output impedance of .5 mohm?

I'm not mesure this, test stereoplay magazin march 1989, but audio precision can do it.

 

[microstrip]

470uf has only 0. 1uf /101 ohms after 38years leaky underneath

Ok, thanks - as expected it was not a 470 uf capacitor any more since long ...

Minium load that can drive the amp at the speaker output before it goes in protection with full power..

Ok. Surely it is not in class A, it changed to class B at a much lower power.

I'm not mesure this, test stereoplay magazin march 1989, but audio precision can do it.View attachment 146979

As far as we can see damping is low, as expected in a probably low feedback class A - around 13 and 50 , not 15000.

 

[Atmasphere]

Still pisses me off the one 845 amp is microphonic.

If it really is microphonic that's usually a tube problem. I don't recall- did you swap the tubes left for right and what happened when you did?

 

[DasguteOhr]

Ok, thanks - as expected it was not a 470 uf capacitor any more since long ...



Ok. Surely it is not in class A, it changed to class B at a much lower power.

Complete class a 407 watt at 0.6 ohm clipping point.

As far as we can see damping is low, as expected in a probably low feedback class A - around 13 and 50 , not 15000.

This was exsample pic from audio precision not from the amp, i have sayed i'm not mesure DF of the amp.

 

[microstrip]

Complete class a 407 watt at 0.6 ohm clipping point.

Not possible - this would need around 30A bias current.

This was exsample pic from audio precision not from the amp, i have sayed i'm not mesure DF of the amp.

Your example shows something that can be measured easily. Again a
damping factor of 15000 is not easily measured and can't be trusted unless documented.

 

[DasguteOhr]

Not possible - this would need around 30A bias current.



Your example shows something that can be measured easily. Again a
damping factor of 15000 is not easily measured and can't be trusted unless documented.

You can believe me or not. Anyone who writes something like that on the back of their product is sure of what they are saying. This is the most load-stable amp I know.
Here you can buy it a pair for 3.8k€ mesure it self the" gravestones" a legendary.

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Wichtig: Beide Endstufen haben einen Regler der bei null Last, also kein Signal, die Endstufe in denStandby-Modus schaltet um Strom zu sparen. Bekommt die Endstufe wieder ein Signal schaltet er die Endstufe wieder in den Betrieb.

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[Alrainbow]

Not possible - this would need around 30A bias current.



Your example shows something that can be measured easily. Again a
damping factor of 15000 is not easily measured and can't be trusted unless documented.

You can’t fix someone who thinks any amp is still in class A bias at 400 watts and at .6 ohms . I have a few high class A bias Amps
none get close to this rating.
Krell ksa200 is close to 100 watts at 16 amps idle
Ml no 33 is a bit higher but math says 8 ohms full bias
4 ohms is half of class a at 8 ohms
2 ohms is half of 4 ohms
a simple way to get an idea of class a is measure idle current
Increase signal to amps input
When the amp input current changes it’s no longer in class a
this change occurs faster as speaker imp is lower.

 

[DasguteOhr]

You can’t fix someone who thinks any amp is still in class A bias at 400 watts and at .6 ohms . I have a few high class A bias Amps
none get close to this rating.
Krell ksa200 is close to 100 watts at 16 amps idle
Ml no 33 is a bit higher but math says 8 ohms full bias
4 ohms is half of class a at 8 ohms
2 ohms is half of 4 ohms
a simple way to get an idea of class a is measure idle current
Increase signal to amps input
When the amp input current changes it’s no longer in class a
this change occurs faster as speaker imp is lower.

That thing delievers 60 ampere at the speaker terminals. That why the biggest mundorf pure copper clamps in there.
You need 2 resistors to mesure it

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Unfortunately, Mr. Schäfer (SAC) passed away in 2017. As far as I know, the company no longer exists. He created wonderful devices such as the SAC Epsilon Accu Preamp, which can drive low-impedance headphones at the preout.

 

[Folsom]

Thanks. Can you point a link to a 120mm Be Quiet model that is more silent than the equivalent Noctua - e.g. https://noctua.at/en/products/fan/nf-a12x25-5v-pwm?

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[LL21]

I think the Noctua still wins? Here is their list of 120mm some of which produce 107.5 m3h of airflow while only making 17.8db of noise? The besilent is 82.7 m3/h of airflow and 18.9db of noise. the super quiet bequiet that is 15.7db of noise only hits 65 m3/h of airflow.

 

[Kingrex]

If it really is microphonic that's usually a tube problem. I don't recall- did you swap the tubes left for right and what happened when you did?

Many times. It's the amp. The microphonics as I call it, or hyper sensitivity always stays with the amp. I had to damp the chassis to some degree to shut it down. If you lightly tap the input or driver tube, it's a loud clank out through the speakers. This is with 1 amp only. The other amp does not do this. And I have swapped the tubes. Many times. It's never deviates from the one amp. The manufacturer thinks it's a bad solder joint. I think it's a persistent problem that was always there and was never resolved because the tech that worked on them only altered one amp to be up to current design. It's a clearly different circuit design between the 2 amps.

It pisses me off as I actually like the amps now. The performance is quite good. The Electroprint output transformer is blended well. The new input transformers from the manufacturer are much more quiet. The circuit seems to be good, in one amp. They play very well. They drive my PAP Trio 15 speakers with no issue. They have some body that may be a little added flavor. But its very pleasant. My KT88 amps have a little more crack and percussion when a snare drum hits. But I like the warmth and body in the bass from the 845.

I may have to send them to you Ralph. I just hate to spend $800 to ship amps around. I should just drive them to Portland OR and have the guy that started them complete them. He did decent enough work on the one he finished.

 

[MarkusBarkus]

...would a bad joint show up in IR, assuming you have a FLIR or similar device, and the boards are accessible?

 

[Kingrex]

...would a bad joint show up in IR, assuming you have a FLIR or similar device, and the boards are accessible?

Hmmm. Good suggestion. I have a heat laser probe. Not a FLIR.

 

[MarkusBarkus]

...and I honestly don't know, Rex. But I wonder if such an investigation might reveal anything. Good Luck if you get into it.

 

[Folsom]

I think the Noctua still wins? Here is their list of 120mm some of which produce 107.5 m3h of airflow while only making 17.8db of noise? The besilent is 82.7 m3/h of airflow and 18.9db of noise. the super quiet bequiet that is 15.7db of noise only hits 65 m3/h of airflow.

View attachment 147055

The Silent Wing 4 has 50% increased static pressure. That means that the Noctua when anything but open air situated, suddenly flows less. Also type of sound matters too - the frequency characteristics can mean more.

A lot of these applications only need air, they don't necessarily need much.

When you build PCs and try different fans and enclosures, the quietest is not always what you think it will be. In fact a ton of "quiet" products are noisy.

 

[Holmz]

Now that plastic straw are a thing again…

Or some plastic stick like a p-tex stick for ski repairs, and some rubber gloves; and then pokin-n-probing might help to narrow down where the problem joint is at?

 

[LL21]

The Silent Wing 4 has 50% increased static pressure. That means that the Noctua when anything but open air situated, suddenly flows less. Also type of sound matters too - the frequency characteristics can mean more.

A lot of these applications only need air, they don't necessarily need much.

When you build PCs and try different fans and enclosures, the quietest is not always what you think it will be. In fact a ton of "quiet" products are noisy.

Interesting! So we have 2 places for Noctua. We placed our own on top with a temperature sensor and they automatically turn on and off...so I guess you would call that open air since they are resting on top. Those are SUPER silent.

The Robert Kodas then have their own in-built Noctuas underneath the amps that blow UP. You CAN hear those and Robert and I sometimes discuss whether there are any other fans coming out that would do the same cooling job but more quietly. He said its about air movement as much as anything else in terms of noise.

I wonder whether these would be better? He said he has ordered and trialed at least a dozen fans before settling on the Noctuas.